Due to the following problems pronging on the skewer has been typically performed by hand so far:                the individual ingredients differ in shape and size        the individual ingredients differ in hardness and toughness        the skewers are not always straight        the skewers are instable in transversal direction        
Even a partial automation of the production process has only taken place in as far as pronging the individual ingredients along a conveyor belt was distributed between different manual laborers so that each laborer prongs a particular ingredient in a particular position in the sequence of the ingredients on to the skewer.
Besides that solutions are known in which a robot supports a skewer and prongs the ingredients one after another that are provided on a conveyor belt out of sequence, and/or the ingredients are conveyed in channels and pronged by hand.
However the complexity is much too high in relation to the output actually achieved.